1. Field of the Invention
The present invention relates to a clip assembly that couples a thermal element to an integrated circuit package and a printed circuit board.
2. Description of Related Art
FIG. 1 shows an electrical assembly of the prior art sold by Intel Corp. The assembly includes an integrated circuit package 1 that is soldered to a printed circuit board 2. The package 1 contains an integrated circuit (not shown) which generates heat. The assembly is provided with a thermal element 3 to facilitate the removal of heat from the package 1. The thermal element 3 is typically a heat sink which has a plurality of pins 4 that extend through the printed circuit board 2. The thermal element 3 is fastened to the circuit board 2 by a spring 5 that is attached to the pins 4. There are typically two springs in the assembly. The assembly is designed so that the springs 5 have a pre-load which pulls the thermal element 3 into the package 1. A thermal grease (not shown) is typically located between integrated circuit package 1 and the thermal element 3 to minimize the thermal impedance between the two components 1 and 3.
The assembly is typically incorporated into to a computer which may be subjected to external shock and vibration loads. It has been found that such external loads may create a physical separation between the thermal element 3 and the package 1. Any separation will increase the thermal impedance between the element 3 and the package 1 and increase the junction temperatures of the integrate circuit. Additionally, relative movement between the thermal element 3 and the package 1 may "pump" the thermal grease out of the thermal interface. The reduction in thermal grease also increases the thermal impedance of the package/thermal element interface and the junction temperatures of the integrated circuit.
The assembly is designed so that the springs 5 apply a pre-load which pulls the thermal element 3 into the integrated circuit package 1. The pre-load forces F are transferred into the printed circuit board 2 through a pair of support points of each spring 5. The load transfer points are located beneath the integrated circuit package 1. These point loads create localized high stress points which can crack some of the solder joints of the package. Cracked solder joints may create electrical shorts which effect the operation of the integrated circuit. It would be desirable to modify the assembly shown in FIG. 1 to prevent separation between the thermal element and the integrated circuit package and to minimize the stresses on the solder joints of the package.